Electric blasting-machine.



E. W. DAVIS.

ELECTRIC BLASTING MACHINE.

APPLICATION FILED SEPT- 28' I914.

Patented Dec. 19, 1916.

UNITED STATES PATENT oEEIoE.

ERNEST W. DAVIS, OF CHICAGO, ILLINOIS, ASSIGNOR TO TI-IE AE'INA. POWDER COM- I P ANY OF CHICAGO, ILLINOIS, A CORPORATION OF INDIANA.

ELECTRIC BLASTING MAC INE.

Specification of Letters Patent.

Patented Dec. 19, 1916.

Application filed September 28, 1914. Serial No. 863,968.

5 ing an armature and anelectro-magnetic fieldwith one or more relays for the purpose of altering the circuit when certain conditions in the speed of the armature and magnetic intensity of the field occur.

One relay which will be designated hereinafter as the line relay is connected in the circuit in such manner that the current generated in the armature of the dynamo is shunted through an external circuit when the line relay is sufficiently energized. The other relay which will be known hereinafter as the field relay is connected with the field winding of the dynamo. When this field rela is s'ufiiciently energized it closes and there y decreases the resistance in the field circuit. It has been found advantageous to surround the cores of both line and field relayswith inductive conductors for the purpose of delayin of these relays as will beexp lained more fully hereinafter. j The armature shaft of the dynamo is preferably supplied with a fiywheel for the purpose of maintaining the speed of the armature when the field relay is closed. The closing of the field relay causes an increase in the magnetic intensity of the field which produces a sudden increase in the load, and

\ it is for the purpose of supplying power for tliissudden increase in load that the fly wheel is supplied.

The preferred embodiment of my invention is illustrated in the accompanying o drawings in which a Figure 1 is a front elevation of the complete machine showing the dynamo and both line and field relays. Fig. 2 is a side eleva: tion and shows the dynamo with the fly wheel on the armature shaft. Fig. 3 is the preferred system of wiring. Fig. 4 is a the release modification of the wiring shown in Fig.3. Fig. 5 is the line relay, which is'the same as the field relay except that the field'relay is wound with finer wire.

The dynamo comprises a field having field windings 6 and 7 and an armature 8. The armature shaft is provided with a fly wheel .9, which is preferably of large diameter in order that its moment of inertia shall be great enough-to carry the temporary load while the machine is discharging at its greatest capacity, i

The line relay 10 com rises a magnet 11 and armature 12 (Fig. 1 The magnet 11 consists of a core 13, (Fig. 5) having paramagnetic end pieces 14 and a winding 15. Contact is made between the end pieces 1 1 and the armature 12, both of which are connected in the circuit in the manner illustrated in the wiring diagram Fig. 3.

' In the Wiring diagrams, (Figs. 3 and .4)

which are purely diagrammatic, relays of the conventional type are shown having contacts separate from the cores. Theyv are shown in this manner for the sake of clearness and in order to facilitate tracing the circuit. The specific construction of the relays is that shown in Fig. 5. The core 13 is" surrounded by an inductive conductor which consists of a copper tube 16. Any decrease in the magnetism of the core 13 induces a current in the copper tube 16', and

this induced current is in such a direction that it tends to maintain the magnetism of the core 13. This produces a delayed action of the relay 10 and improves the action of the machine for reasons whichwill be described hereinafter. The field relay 17 is identical with the line relay 10, except that the wire helix is of finer wire and contains a greater number of turns.

shown in Figs. 1 and 2. A very weak cur-.

rent is thus produced which passes from the brush 21 (Fig. 3) through the field wind ings 6 and 7 and field relay 17 back to the brush 22. The resistance/of the field relay 17 isvery high, so that very little energy is Binding posts 18 and 19 are provided for the purpose of required to revolve the armature 8 while the field relay 17 is open, but as the rotation of the armature 8 is gradually accelerated the E. M. F. is gradually increased and when the proper speed is reached the field relay 17 is closed. The E. M. F. then 1ncreases very rapidly until the line relay 10 closes, thus allowing the current to pass out over the line and fire the detonators 20. During the interval between the closing of the two relays the load on the dynamo 1s very strong and in a large machine it would be impossible for a man of ordinary strength to turn the crank 23 fast enough to maintain the necessary speed, but the fly wheel 9 by virtue of its momentum continues to rev'olve the armature at -a very slight decrease in speed until the line relay 10 has closed and until electric detonators 20 have been fired. With this .machiiie a man of ordinary strength can produce a current of 800 watts, or over one horse-power. This is due to the fact that energy is supplied for a considerable. length of time and stored in the fly wheel and later converted intoelectrical energy during a much shorter period of time.

The construction of the relay shown in Fig. 5 is particularly adaptable to this in vention. As the armature 12 approaches the end pieces 14 the attraction'increases, and when these parts are in contact acompara- .tively weak current in the relay winding is sufiicient to hold them in contact. For this reason the induced current in the copper tube 16 is suflicient to hold the armature 12 in contact with the end pieces 14 for a small period of time, even when the current flowing through the winding 15 has ceased. It

has been found by actual practice that a relay without the inductive conductor 16 causes a chattering motion of the armature 12 which makes the operation of the machine uncertain.

. In the wiring diagram illustrated in Fig. 4 a low resistance 28is placed in a circuit in such manner that it is shunted across the closed and the machine will still be opera" tive, provided suflicient power is applied to rotate the armature when the resulting heavy current is fiowingthrough field "Win'dings. suficient power can be applied by'hand to revolve the armature with the field fully magnetized, and in 'machines designed to fire but a few detonators the field relay 17 may be omitted.

In the improved machine which has been 7 speed.

Obviously in a very small machine.

described the discharge has more of the nature of a direct current, the drop in potential being comparatively slow and the duration of the discharge comparatively long.

Prior attempts to use a current taken directly from an armature of a dynamo have been unsuccessful in large, hand operatedmachines because of the limited power that can be obtained by turning a crank, but in the device of this invention the, power is supplied for such a longtime relative to the. time during which the discharge takes place,

that it produces a stronger current that machines of the inductive discharge type.

In the device of this invention the discharge through the external circuit cannot occuruntil the machine is working at its greatest capacity. The advantage of this action will be apparent to any one familiar with blasting operations.

I claim:

1. The combination with a dynamo com: prising an armature and an electro-magnetic field, of a line relay energized by current. from said dynamo and connected in such' manner that the current generated by said armature is shunted through anexternal cirout when saiddine relay is suificiently energized, the core of said line relay being surrounded by an inductive conductor whereby the release of said line relay is delayed, thus prolonging the discharge through said extei'nal circuit.

' 2. The combination with a dynamo comprising an armature and an electro-magnetm field, of a line relay connected in such manner that the current generated by said armature is shunted through an external circuit when said line relay is sulficiently energized, andmeans for automatically decreasing the resistance of the field circuit of said dynamo when said armature has attained a given 3. The combination with a dynamo -comprisingan armature and an' electro-magnetic field, of a line relay connected in such manner that the current generated by said armature is shunted-through an externalcircuit when said line relay is sufficiently energized, and a-field relay connected with the field winding of said dynamo ,and arranged to decrease'the resistanceof the fieldcircuit of said dynamo when said field relay is sulficiently energized; I

4. The combination with a dynamo com- '-prising an armature and an electro-magnetic and a field relay connected with the field winding of said dynamo and arranged to supply current to said line relay when said field relay has been sufiiciently energized,

the core of said field relay being surrounded by an inductive conductor whereby the re lease of said field relay is delayed.

5. The combination with a dynamo comprising an armature and an electro-magnetic field, of a line relay connected in such manner that the current generated by said armature is shunted through an external circuit when said line relay is sufiiciently energized, and a field relay connected with the field winding of said dynamo and arranged to decrease the resistance of the field circuit of said dynamo when said field relay is sufficiently energized, the core of said field relay being surrounded by an inductive conductor whereby the release of said field relay is delayed.

6. The combination with a dynamo comprising an armature and an electro-magnetie means comprising a fly wheel or other in-' ertia member arranged to impart its motion to said armature.

In testimony whereof I afiix my signature in the presence of two witnesses.

ERNEST W. DAVIS. Witnesses R. J. WARREN, J. L. MALONE. 

